New ultrasound of Charlotte the 'virgin stingray' shows her pups alive and well in the womb - and she could give birth ANY DAY

Charlotte the stingray took the world by storm when a North Carolina aquarium announced her immaculate conception in early February.

Now, the Aquarium & Shark Lab in Hendersonville has released an ultrasound video of her pups moving their tails inside her womb and confirmed it will release more information tomorrow.

The team has previously said they don’t have a specific due date for the virgin stingray because an immaculate conception has never been observed in the animals before, but said she is pregnant with up to four pups and is expected to give birth soon.

Charlotte the stingray is expected to give birth any day now

The team at the Aquarium & Shark Lab in Hendersonville showed an ultrasound of the pups moving their tails inside Charlotte's womb

The aquarium's uncertainty over when Charlotte is due to give birth stems from the team’s inability to know exactly when she conceived, particularly because ultrasounds for stingrays are usually conducted in late-term pregnancies.

The cause of her pregnancy was also a mystery because there weren’t any male stingrays in the aquarium with her, but experts said it was most likely attributed to parthenogenesis – the scientific term for virgin birth.

When this happens, the stingray develops a cloned embryo of itself, which can happen when the mammal has been in isolation for a lengthy period of time.

The Aquarium & Shark Lab suggested Charlotte could have been impregnated by a shark, but experts said that's impossible

Stingray experts say Charlotte's 'miracle birth' is most likely due to parthenogenesis - a scientific term for virgin birth

‘They can become pregnant without observed mating with a male in two ways,’ Dr. Christopher Lowe, a professor of marine biology and director of the Shark Lab at California State University told Dailymail.com last week.

The first is that ‘many species of sharks and rays can store sperm for at least up to one year,’ but Lowe said it is unlikely because Charlotte has been on her own for too long.

‘Turns out that parthenogenesis is more common in sharks and rays than we previously thought, so this is the most likely explanation,’ Lowe said.

Depending on the water's temperature, the average stingray’s gestation period is about three to four months.

Certain animals are capable of reproducing through 'facultative parthenogenesis' in which the egg is fertilized with cells from the mother rather than by a male 

Researchers say Charlotte's ultrasound shows she's carrying up to four pups

Mercedes Burns, an assistant professor of biological sciences at the University of Maryland, told Dailymail.com that because Charlotte’s pregnancy appears to have proceeded normally, she expects the stingray will give birth in another month or so.

‘The interesting thing about Charlotte is she represents the first time for her species that parthenogenesis has been documented, making it the 15th species where parthenogenesis has been documented in an elasmobranch,’ Kevin Feldheim, a researcher at Chicago’s Field Museum who is a parthenogenesis expert told Dailymail.com.

READ MORE: What is a virgin birth? Step-by-step graphic reveals how a female stingray was able to get pregnant - despite living alone 

Certain animals like sharks and snakes are capable of producing healthy offspring without ever mating, through a process known as parthenogenesis. 

Elasmobranch includes a variety of cartilaginous fish species – mammals that have between five and seven gill clefts – including sharks, rays, skates, and sawfish.

Shortly after the aquarium announced Charlotte’s pregnancy, it speculated that she could have become impregnated by a white-spotted bamboo shark that was reportedly living in the tank with her, something experts have said is impossible.

‘The more and longer some species are kept in captivity the more we learn about oddities like this,’ Feldheim said.

‘But there is no way the ray was impregnated by a shark. That’s just not possible.’

Experts have only studied parthenogenesis in sharks and stingrays for just under two decades, and although both are Elasmobranchs, Warren Booth, an associate professor of entomology at Virginia Tech told NPR that ‘it’s very unlikely.’

He added: ‘I think they're so genetically distant that that is not considered possible.’

However, he added that the pups could have problems when they’re born if they were conceived through parthenogenesis.

‘Parthenogenesis has a tendency to produce offspring that are not very healthy,’ Booth told the outlet.

‘In all of the studies in snakes, birds, and sharks, the offspring don't survive very long. They're stillborn or they expire within a short amount of time.’

Lowe said ‘a quick DNA test will confirm if the female produces viable young.’

NPR reported that the Field Museum of Natural History in Chicago will be conducting a DNA test on Charlotte and her pups once they’re born to conclusively show how the stingray got pregnant.